Author Topic: Canít connect to Vaisala WXT520 service port  (Read 45 times)

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Offline sidtupper

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Canít connect to Vaisala WXT520 service port
« on: November 26, 2020, 04:36:09 PM »
Iím having difficulty communicating with a Vaisala WXT520 weather station over a RS232 connection.

The station has a 4-pin service port (Vin = 4.5v measured, GND, TDX, RDX).  I made a cable for it based on a pin-out diagram I got from Vaisala.  The instrument needs > 6v so Iíve provided 12v to the Vin pin in the 8-pin data port connector.  The manual says thatís ok.

Iíve connected the instrument with the 2m cable to a USB to serial adapter plugged into a laptop.  The service port wants COM1 so I used Device Manager to rename the PC com port to COM1 and set the communication parameters (19200, 8, none, 1) as specified in the manual.   Then I tried to send a command string 0XU to the station with Putty.  No response, not even my keystrokes echoed to the terminal.  Checked the cable continuity; itís fine.  I tried shifting the pins around and found a permutation that lights both the TDX and RDX leds on the serial adapter and echoes my Putty input but doesnít return a response from the station.  Then I tried all 24 permutations of the 4 pins and found three interesting ones, two with the result just described, and one which lights only the RDX led and vomits continuous screenfuls of this repeating sequence: -u▒▒▒T▒▒T▒v▒▒ .  None of these three permutations matches the pin-out.

I tried to confirm the service port pin-out by looking for continuity between the service port pins and the labeled data port pins on the bottom board, without much success.  The service port Vin connects with the data port Vin- but the Rx, Tx and GND donít connect with anything in the header on the bottom board.

Iíd be grateful for suggestions on a way forward.  Vaisala tech support says they have stopped supporting the WXT520 and wonít help.
« Last Edit: November 26, 2020, 04:37:55 PM by sidtupper »